1. Field of the Invention
The present invention relates to a cleaning device incorporated in an electrophotographic image forming apparatus such as a copier, a printer, and a facsimile. In addition, the present invention also relates to an image forming apparatus and a process cartridge using the cleaning device, and a toner used in the cleaning device.
2. Discussion of the Background
An image forming apparatus, which uses an electrophotographic process, includes a photoconductor as an image bearing member, and operates to charge the surface of the photoconductor by discharging, to form an electrostatic latent image on the surface of the photoconductor by exposing, to develop the latent image by supplying toner to the surface of the photoconductor, to transfer the developed toner image onto a sheet, to fix the developed image on the sheet, and to then output the sheet. After transferring the developed image to the sheet, the surface of the photoconductor is cleaned with a cleaning device so that any residual toner does not exert a negative influence on the next image forming process. As a cleaning device, a cleaning blade including elastic bodies, such as rubber, to remove incrustations such as remaining toner is generally known.
Also, to enhance image quality, smaller diameter and higher roundness toner is being intensively designed at present. The purpose of using such toner is to make the toner bond to the electrostatic latent image more closely.
However, as known by those skilled in the art, high roundness toner has a poor cleaning characteristic in general. When such high roundness toner is cleaned up with a rubber blade, which is conventionally used to clean pulverized toner, it is difficult for the rubber blade to catch the high roundness toner particles at the blade edge thereof because of tumbling of the round particles. As a result, the high roundness toner particles tend to pass through the rubber blade. In addition, when such a cleaning blade is used, the life of the photoconductor surface shortens by wearing.
Thus, a technique that applies a lubricant to the photoconductor has been adopted to reduce frictional resistance between the photoconductor and cleaning blade, and to address a malfunction such as wearing of the cleaning blade. In addition, when a lubricant is applied to a photoconductor surface, the lubricant can prevent outbreak of so-called “filming” by reducing a coefficient of friction of the photoconductor surface. “Filming” is a phenomenon in which a fluidity agent or charge control agent added externally to the toner adheres to the photoconductor by abutment pressure with a cleaning blade. In addition, the reduction of adhesive power of the toner developed on the photoconductor with a photoconductor surface improves the transfer characteristics.
As for a mechanism to apply the lubricant to the photoconductor surface, for example, a solid lubricant made of such as fatty acid metal salts in the shape of a stick can be installed. And a brush roller is arranged to abut with the solid lubricant and photoconductor. By the lubricant application mechanism, the rotationally driven brush roller scrapes the solid lubricant, and supplies fine-grained lubricant to the surface of the photoconductor. Then, when the surface of the photoconductor is in contact with the cleaning blade, the lubricant is spread in a thin film to lower the frictional coefficient of the surface of the photoconductor.
However, when a residual toner on the surface of the photoconductor bonds to an application brush of the lubricant application mechanism, application efficiency of a lubricant deteriorates. Also, lubricant application is not stable, and thus it becomes difficult to address the above problem. In addition, the unstableness of an application quantity of a lubricant applied to a photoconductor surface produces unevenness of application, causes cleaning defectiveness on a part at which the lubricant is not applied enough, and causes abrasion of a cleaning member such as cleaning blade.
Thus, it is important that the lubricant of an appropriate quantity is applied to a photoconductor surface stably. Japanese Patent Laid-Open No. 10-260614 discloses a method of prescribing a density of fibers of a brush roller applying a lubricant. And Japanese Patent Laid-Open No. 2003-57996 discloses a method of prescribing the pressure of a pressure application member that is pressing the solid lubricant against the brush roller side, and prescribing a quantity of the brush roller sinking into the photoconductor surface.